Restoring post-agricultural land to tropical forest can be challenging, as the pasture grasses tend to choke out the native trees. A new study, however, indicates that waste from the coffee industry gives those trees a fighting chance.
The coffee beans that many of us know and love are contained within a larger fruit known as the coffee cherry. Once a bean has been extracted from its cherry, the rest of the fruit is typically just discarded. That waste product is called coffee pulp.
Back in 2018, scientists from the ETH Zurich research institute and the University of Hawaii spread 30 dump truck loads of that pulp onto a 35 by 40-meter (115 by 131-ft) area of agriculturally degraded land in Costa Rica. As a control, they also marked out an adjacent area of the same size, to which no pulp was applied.
After two years, it was found that the 80 percent of the treated area had been covered with the canopy of a native forest that had grown on the land. By contrast, the control area only had a 20-percent canopy cover, with the rest of the land being dominated by the non-native pasture grasses that had originally been introduced by farmers. What's more, the trees that did grow in the control area were only one quarter the height of those that grew on the treated land.
The scientists believe that the 0.5-meter-deep (1.6-ft) layer of coffee pulp smothered much of the grass which would otherwise have taken over. At the same time, though, the pulp boosted carbon, nitrogen, and phosphorous levels in the underlying soil. As a result, when tree seeds were dispersed into the area either by the wind or in animal feces, they were better able to grow.
Plans now call for longer-term studies to be conducted on larger areas of land, perhaps utilizing other types of agri-waste such as orange husks.
"This case study suggests that agricultural by-products can be used to speed up forest recovery on degraded tropical lands," says the lead scientist, U Hawaii's Dr. Rebecca Cole. "In situations where processing these by-products incurs a cost to agricultural industries, using them for restoration to meet global reforestation objectives can represent a 'win-win' scenario."
A paper on the research was recently published in the journal Ecological Solutions and Evidence.
Source: British Ecological Society